Functional Overview

The SHFLI Lock-in Amplifier consists of several internal units that process digital data (light blue color) and several interface units processing analog signals (dark blue color). The front panel is depicted on the left-hand side and the back panel is depicted on the right-hand side. The arrows between the panels and the interface units indicate selected physical connections and the data flow.

The orange blocks are optional units that can be either ordered at purchase or upgraded later, while the grey shaded ones represent features that will be implemented in the future. The SHFLI Lock-in Amplifier has 2 physical channels each with its own signal input and output, auxiliary input and digital inputs and outputs. The ordering guide details the currently available upgrade options.

The signal to be measured is usually connected to one of the two SHFLI signal inputs where it is amplified to a defined range and mixed down to an intermediate frequency (IF) through a double-superheterodyne scheme and digitized at very high speed if above 800 MHz, or directly digitized if below this frequency threshold. The resulting samples are fed into the digital signal processor that contains 8 dual-phase demodulators. The results of the demodulation are fed into a digital interface to be transferred to the host computer through the LAN or USB interface, and can also be routed to the auxiliary outputs on the front panel of the SHFLI. Two low-distortion signal outputs provide the signal generator functionality.

The numerical oscillators generate sine and cosine pairs that are used for the demodulation of the input signal and also for the generation of the SHFLI output signals. For this purpose, when the SHFLI-MF Multi-Frequency option is present, the Output Adder can generate a linear combination of the oscillator outputs to generate a multi-frequency output signal. After the digital-to-analog conversion, the output signal is either routed directly to the output connectors, if its final frequency is below 800 MHz, or through the double-superheterodyne upconversion path if its final frequency needs to be above this frequency.

Hardware trigger and reference signals are used for various purposes inside the instrument, such as triggering demodulation and oscilloscope data acquisition, to acquire or generate an external reference signal, or triggering other equipment.

The front panel SMA connectors and control LEDs are arranged as shown in Figure 2 and listed in Table 1.

The back panel is the main interface for power, control, service and connectivity to other ZI instruments. Please refer to Figure 3 and Table 2 for the detailed description of the items.

Table 3 provides an overview of the available SHFLI products. Upgradeable features are options that can be purchased anytime without the need to send the Instrument back to Zurich Instruments.

¹ Requires UHF-MF Multi-frequency option

² Available by end of 2023